Dr VIRAF. J. DALAL Solutions for Chapter: Elements, Compounds & Mixtures, Exercise 1: EXERCISE

Classify substances into pure and impure substances in the form of a chart or tabulation. 

Differentiate between the terms elements, compounds and mixtures. 

The important physical properties of substances are colour, odour, nature, density and solubility in water. Name -

a) two coloured gases (with their colours) 

b) a gas with a pungent, choking odour which is lighter than air

c) a poisonous gas almost as heavy as air. 

Draw a labelled diagram of an atom including its nucleus, orbits and their contents. 

An atom of an element is denoted by a 'symbol'. Explain the meaning of the term 'symbol'. State a reason for representing the following elements by their symbols.

a) Hydrogen by $\mathrm{H}$

b) Helium by $\mathrm{He}$

c) Copper by $\mathrm{Cu}$

Write the formula of the compound formed - given symbols and combining power or capacity (valency) of each element in the compound.

${\mathrm{Ca}}^{2+} {{\mathrm{NO}}_3}^{1-}$

Match the formulas of the following gases with their correct names.

Gases - a) ${\mathrm{H}}_2$ b) ${\mathrm{N}}_2$ c) ${\mathrm{O}}_2$ d) ${\mathrm{Cl}}_2$ e) $\mathrm{HCl}$ f) ${\mathrm{NH}}_3$ g) $\mathrm{CO}$ h) ${\mathrm{CO}}_2$ i) ${\mathrm{SO}}_2$ j) $\mathrm{NO}$ k) ${\mathrm{NO}}_2$

Names - 1. Ammonia 2. Nitrogen dioxide 3. Oxygen 4. Hydrogen 5. Nitrogen 6. Chlorine 7. Carbon monoxide 8. Sulphur dioxide 9. Nitrogen monoxide 10. Carbon dioxide 11. Hydrogen chloride.

In the chemical word equation:

Zinc $+$ Sulphuric acid $\to$ Zinc sulphate $+$ Hydrogen

a) State the reactants and products of the above reaction. What does the arrow indicate?

b) The molecular equation is $\mathrm{Zn} + {\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{ZnSO}}_4 + {\mathrm{H}}_2\left[\mathrm{g}\right]$. State what [g] represents?